Great Moments in Packaging: No 7 – Kraft paper
As well as having one of the finest rhyming names in packaging history, Carl Dahl (oh, what fun his school friends must have had!) stands out as one of the giants in our field. For in 1879, Carl F Dahl (as he is more commonly, but less amusingly referred to) invented the kraft process in papermaking. As a result we have brown kraft paper rolls and sheets, which give us a practical, strong and extremely presentable packing and gift-wrapping solution, beautiful retail paper bags, and, using kraft paper in its corrugated form, a key part of many cardboard boxes.
What Dahl’s invention did was to convert wood into wood pulp which consisted almost entirely of cellulose fibres. He did this by treating the wood chips with white liquor (a mixture of sodium hydroxide and sodium sulphide), as a result breaking the bonds linking the lignin to the cellulose. Clever, eh?
In case you’re wondering, lignin is a complex chemical compound predominantly found in wood. It is also one of the most abundant organic polymers on earth. Wood with a lot of lignin in is highly durable, making it an excellent raw material for a lot of applications, and also makes excellent fuel. What it doesn’t do is make strong paper, because its hydrophobic nature interferes with the formation of the hydrogen bonds between cellulose in the fibres. It’s the links between the cellulose that makes the paper strong.
Dahl patented the process in 1884 and you can read his description of it here. If you can understand it, well done. We don’t know much about Dahl himself except that he was Swedish, that he was for some reason in Danzig when he invented the process and that the first mill to use his technique opened in Sweden in 1890.
The recovery position
There is, however, another important name in the history of kraft paper, and that is George H Tomlinson of Quebec. What Mr Tomlinson did was to invent the recovery boiler, which reused the black liquor that is left over from the kraft process. This can be burned for its fuel value, thus providing energy to run the mill, usually with some to spare, which is sometimes fed into the local grid.
As a result, the whole process is extremely efficient, mostly self-sufficient and doesn’t damage the environment. And at the end you get one of the finest packaging materials around!
The Tomlinson patent application can be read here, but we don’t recommend it unless you have a lot of spare time and first class degrees in chemistry and physics.
There are loads of great packaging products at www.davpack.co.uk made from kraft paper, so why not check them out, or call our Customer team on 01332 821200 for more advice on the options available!
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